1. Field of the Invention
This invention relates to an architectural covering, particularly a covering for an architectural opening, such as a window blind or shade.
2. Description of the Related Art
Conventional blinds and shades for windows have included a head rail, a bottom rail, one or more window covering elements extending between the head rail and the bottom rail, at least two lift cords extending from the head rail and supporting the bottom rail, and a mechanism to limit the downward movement or drop of the bottom rail.
For pleated or roman shades, the drop height of the shades has usually been limited by a cord connector, engaging the cord outlet at the bottom of the head rail upon full drop of the bottom rail. Sometimes, pleated and roman shades have also been provided with an additional cord to limit drop. On the other hand, for venetian blinds, the full drop has usually been limited by the full extension of the ladder cords.
Limiting drop, without additional cords, by making use of the lift cord has presented obvious advantages because fewer elements are used in assembling the blinds or shades. Experience has shown, however, that providing the proper effective lengths of the lift cords between the head rail and the bottom rail for controlling drop has not always been easy. Conventional shades have had a minimum of two lift cords co-extending through the shade members and holding the bottom rail at several locations spaced along its length. The free ends of these lift cords have extended through the head rail to an exit opening or cord lock in one of its longitudinal ends, and the free ends have optionally been joined or knotted together in a cord connector outside the head rail. The effective length of the lift cords might be the length of the cords as they extend between the head rail and the bottom rail or from the cord connector to the bottom rail. The effective length of the lift cords determines the orientation of the bottom rail relative to the head rail.
Accurate adjustment of drop has also been important because the bottom rail should not hit the window sill, nor should it be suspended too high, so that an unsightly gap exists between the bottom rail and the window sill. However, it has not always been easy to set precisely the drop by adjusting the final location of a knot along the lift cords, at least prior to making the knot.